It has become a preferred procedure to use staples for wound closure rather than thread or filament sutures. Surgeons choose staples because of the speed with which an incision can be closed as compared with the time consuming placing and tying of thread or filament sutures.
Many surgical staplers have been designed with various features to improve the profile of the stapler to increase visibility for the surgeon during the placing of the staples and to improve the reliability of the stapler with respect to serial delivery of contained staples without jamming. See, for example, U.S. Pat. Nos. 4,014,492, 4,109,844, 4,179,057, 4,202,480, 4,256,251, 4,375,866, 4,407,286, 4,489,875 and 4,527,725. The above patents describe staplers using preformed staples without a forming anvil, staplers having a stationary forming anvil, and staplers having a movable or retractable forming anvil as well as a wide variety of feeding mechanisms to deliver each staple to the delivery point where the staple is deformed during implantation into the skin and/or tissue.
In the effort to increase the angle formed between the bottom of a stapler and the skin or tissue surfaces being joined for the purpose of improving visibility for the surgeon, it has become increasingly difficult to retain jam-free delivery of the staples, particularly in those staplers where the staples are stored on a covered retaining track or rail and fed serially thereon to the forming jaws and forming anvil. The increased angle of the stack of staples stored in such a feeding mechanism of a stapler and the pressure of the biasing means, e.g., a spring biased pusher, tend to cause the stack of staples to buckle and jam the stapler, i.e., a following staple tends to push under a leading staple like a wedge and cause a jam in the feeding mechanism. The present invention provides a novel structure to prevent this problem as explained more fully hereinafter.